Mulford’s milkvetch research update

It takes a full day of driving from western Oregon to reach the closest populations of Mulford’s milkvetch (Astragalus mulfordiae) in the Owyhee Uplands of Malheur County. This rare species occurs in scattered populations in rangelands of Oregon and southwestern Idaho, mostly on sandy soils on rolling hills, flats and near the Owyhee and Snake Rivers.

This is cattle country, with a long history of people living on the land. But what is the effect of cattle on populations of this plant that is considered endangered by the state of Oregon and a species of concern by the US Fish and Wildlife Service? Are cattle and sheep a threat to the species’ survival, or is rangeland grazing compatible with viable, sustainable milkvetch populations?

Mulford's milkvetch is a rare plant of rangelands in eastern Oregon and southwestern Idaho.

This project involves caging Mulford's milkvetch to protect them from livestock.

Since 2008, IAE biologists have partnered with the Bureau of Land Management on a long-term study to evaluate the effects of cattle and sheep on the species, and document population and habitat trends in wild populations. The project involves comparing the growth and survival of plants in plots protected from grazing with plants that are open to animal use, and this design is repeated at six different sites in Oregon. Protected plots are covered with a hog wire cage to prevent ungulate grazing, while still allowing for rain, sun, and smaller animal activity. Biologists map, measure and record animal grazing on all the plants in the plots each year.

So far, caging plants to protect them from large herbivores has had localized effects. For example, in 2016, plants had greater diameter on average in cages, but this effect differed from site to site. At one site where the effect was conspicuous, Snively Creek, caged plants were 40 cm wide while plants exposed to grazers were only 22 cm wide. The same pattern was true for reproduction. Again at Snively Creek, plants produced an average of 221 fruits in cages, but just 41 in uncaged plots. These preliminary results from the study suggest that grazing with livestock may have direct negative effects on this species at some sites and some years, but the effects are variable and complex.

Investigators measure each plant in caged and uncaged plots to document population trends and effects of disturbance.

Mulford's milkvetch prefers sandy soils. Weeds like cheatgrass have become more abundant at all research sites over the course of the study.

In the course of this project investigators have witnessed an overall decline in the number of Mulford’s milkvetch plants at all sites, as well as an increase in the abundance of competitive invasive plants. The decline in plant numbers has been consistent across the landscape, and was particularly pronounced in 2014. In 2010, all sites were dominated by native vegetation except for South Alkali, but by 2015 all sites were exotic-dominated. Invasive plants such as cheatgrass (Bromus tectorum), stork’s bill (Erodium cicutarium), and Russian thistle (Salsola tragus) have steadily increased, which may be an indirect effect of cattle use or other disturbances.

Over the course of this study, weather at the research sites has tended to be drier than the long-term average, which may have contributed to the observed declines. However, winters of 2015 and 2016 were wetter than previous years and more similar to long-term normals, which could explain an uptick in the number of new plants noted in 2015 and 2016. Despite the recruitment of seedlings seen in 2015 and 2016, the decline in Mulford’s milkvetch population numbers observed in the preceding years coupled with the decrease in their size and annual variability in reproductive effort suggest that continued monitoring will be essential for managing for persistence of this species, especially when facing current and ongoing climate changes. In the coming years we will be looking to compare our long-term data set on Mulford’s milkvetch populations in Oregon with data collected in Idaho. In 2017 we will collect the sixth year of consecutive-year data in this long-term project.

Conservation Research News

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The Conservation Research Program at IAE conducts research on propagation methods and how to best ensure survival upon outplanting for a variety of rare species. Often for these projects, we focus on one question or the other separately, but occasionally we have the opportunity to work with a single species throughout the process. Since 2014, […]

We have had many adventures during our Native Plant Society of Oregon internship. In the first week of May, our crew rapidly expanded from the usual 5 to a lively 16, as we were joined in the field by our Executive Director, Tom Kaye, and 10 volunteers from all over Oregon, in order to monitor the population of the endangered Cook’s Desert Parsley (Lomatium cookii), also refereed to as LOCO. Cook’s Desert Parsley is closely related to Lomatium bradshawii, which is an endangered Apiaceae found only in the Willamette Valley. The Institute for Applied Ecology (IAE) has been involved with monitoring the species, habitat, and community at this location for more than 20 years, in partnership with the Medford Bureau of Land Management (BLM) District. It was exciting to be able to contribute to such a long-lasting project that so many people have invested much time and care.

We worked in the Illinois Flats, one of the remaining two population centers of the endangered Cook’s Desert Parsley (the other is north of Medford Plains) (Kagan, 1994). Cook’s Desert Parsley is a small and inconspicuous plant when not flowering; its leaves are narrow and compoundly divided, easily hiding among surrounding vegetation.

The vegetation can be so hard to find, it often means monitoring on your hands and knees with your nose almost in the soil. Sometimes it would take waiting for a small breeze to reveal the hidden Cook’s lomatium, which dips and bends in the wind in contrast to the shaking grasses. Besides being glad to see healthy reproductive plants, we were happy that the creamy yellow umbels made the plants much easier to spot! Thankfully, the icy Illinois River, Deer Creek, and the Cave Junction Dairy Queen were nearby to reward the hot search with a cold treat!

We took a field trip one evening to see the Darlingtonia californica in bloom at 8 Mile Mountain; definitely a highlight of this summer. These incredible carnivorous plants grow in the slowly flowing water of the fen and source nutrients from the rotting insects that fall into their hollow stalk. The insects are lured into the hood by the light shining through the translucent “windows” in the ceiling of hood. Confused by the light, they tumble into the stalk where small downward-pointing hairs prevent them from escaping. The flower of the Darlingtonia is one of the most menacing I have ever seen- the drooping dark purplish-red petals enclosed by large yellow sepals definitely looked the part of a carnivorous plant!

This trip was a great opportunity to tap the impressive collective knowledge of the volunteer crew; we learned from the birding expertise of Marcia, Marisa and Sandy, about Oregon botany from Cindy and our BLM partner Julie, about distance biking in Oregon from the power-couple Wendie and Mike, and about the power of enthusiasm and good vibes from Don. Of course, we also all learned about how to relax at the Siskiyou Field Institute like a true “Duke” from the John Wayne cutout! Thanks to all of the volunteers who endured the heat with us, and to the Siskiyou Field Institute for hosting us at such a beautiful base-camp!

Gallery

An IAE intern, Abbie, showing off her amphibian wrangling skills.

This invasive bullfrog avoided becoming a meal at the Invasive Species Cook-off but some of it’s relatives might not be so lucky!

What is this plant?!?!?

Nadav and our fearless crew leader Meaghan, keying out a tricky trifolium in the field.

Fog on Deer Creek at the Siskiyou Field Institute. A good place for a cup of coffee!

— By Abbie Harold As a Native Plant Society of Oregon Intern with the Conservation Research Program at the Institute for Applied Ecology (IAE) we travel to remote corners of Oregon that are home to rare and endangered plants, some of which are endemic to Oregon. Many of the locations we visit are areas of […]